UIVisualEffectView的错误？

Question

任何人都知道UIVisualEffect视图的错误会导致每个视图的模糊变得更轻/更清晰，添加的视图越多？

我有两个UIVisualEffectViews，其模糊效果很好。一旦我添加了以相同方式配置的第三个UIVisualEffectView，所有它们的模糊突然变得如上所述变亮了？有人遇到过这个吗？或者我做错了什么？

值得注意的是：模糊处于被聚光灯渲染的键盘视图控制器内部。

以下是我的设置代码：

//1

var blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Dark)
        var blurEffectView = UIVisualEffectView(effect: blurEffect)
        blurEffectView.frame = CGRectMake(0, 0, self.frame.width/3-0.5, self.frame.height)
        blurEffectView.opaque = true
        self.addSubview(blurEffectView)

        var vibrancyEffect = UIVibrancyEffect(forBlurEffect: blurEffect)
        var vibrancyEffectView = UIVisualEffectView(effect: vibrancyEffect)
        vibrancyEffectView.frame = self.bounds

        blurEffectView.contentView.addSubview(vibrancyEffectView)
        blurEffectView.contentView.addSubview(btn1)
//2
        var blurEffect1 = UIBlurEffect(style: UIBlurEffectStyle.Dark)
        var blurEffectView1 = UIVisualEffectView(effect: blurEffect1)
        blurEffectView1.frame = CGRectMake(self.frame.width/3+0.5, 0, self.frame.width/3-0.5, self.frame.height)
        self.addSubview(blurEffectView1)

        var vibrancyEffect1 = UIVibrancyEffect(forBlurEffect: blurEffect1)
        var vibrancyEffectView1 = UIVisualEffectView(effect: vibrancyEffect1)
        vibrancyEffectView1.frame = self.bounds

        blurEffectView1.contentView.addSubview(vibrancyEffectView1)
        blurEffectView1.contentView.addSubview(btn2)
//3    
            var blurEffect2 = UIBlurEffect(style: UIBlurEffectStyle.Dark)
            var blurEffectView2 = UIVisualEffectView(effect: blurEffect2)
            blurEffectView2.frame = CGRectMake(2*(self.frame.width/3+0.25), 0, self.frame.width/3-0.5, self.frame.height)
            self.addSubview(blurEffectView2)

        var vibrancyEffect2 = UIVibrancyEffect(forBlurEffect: blurEffect2)
        var vibrancyEffectView2 = UIVisualEffectView(effect: vibrancyEffect2)
        vibrancyEffectView2.frame = self.bounds

        blurEffectView2.contentView.addSubview(vibrancyEffectView2)
        blurEffectView2.contentView.addSubview(btn3)